RESPIRATION And ETHYLENE PRODUCTION

mechanical damage

(during harvesting or postharvest handling) can increase respiration and other metabolic reactions, accelerating the fruit deterioration

Atmospheric composition

- the reduction of oxygen or the increase in carbon dioxide content in the atmosphere surrounding a fruit can reduce its rate of respiration and increase the shelf life of some fresh fruits.

climacteric rise.

As fruit progress towards edibility the respiratory rate increases followed by a decline as fruit senescence.

after

Climacteric fruit ripen ____ harvest, and need not remain on the tree or vine

ripening stage

Climacteric fruits exhibit a high production of ethylene and carbon dioxide at the ___

physiological maturity

Climacteric peak cannot necessarily correspond to the fruit maximum edible quality; however, these fruits must reach their ________ before harvest to develop all desirable characteristics as they ripen.

extrinsic factors

Ethylene production is also promoted by ________________ such as mechanical damages (cuts, bruising, scratches), decay, insect damages, and climate conditions (temperature, relative humidity), as a response of the tissues to different type of stress

rapid and uniform

Ethylene promotes _____ ripening of climacteric fruits (e.g., banana, papaya, tomato) and some nonclimacteric fruit

Atmospheric composition Temperature mechanical damage

Factors affecting Respiration

10'C 2

For every __________ temperature increase, biological reactions involved in the respiration processes are increased by a factor of ____

a. Climacteric b. Nonclimacteric

Fruits can be classified (based on their respiration pattern) into:

anaerobic respiration

However, if the surrounding atmosphere becomes deficient in oxygen, then the metabolic pathways shift and ______________________- occurs.

temperature

In addition to the final products of aerobic respiration (carbon dioxide and water), there is also the evolution of heat.

low and there is no increased evolution rate

In non-climacteric fruits, the general production of carbon dioxide and ethylene gas remains quite ____ of these gases at the ripening stage.

utilization and increase their rate of deterioration.

Other changes, such as sprouting of potatoes and root corps (e.g., onions, garlic, and potatoes), reduce their ___

1. stage of maturity of the fruit 2. water stress 3. Light 4. growth regulators 5. pathological growth 6. chemical stresses.

Other factors which influence the rate of respiration are:

product deterioration.

Physical damage from impact bruising and surface injuries, and pathological breakdown due to bacteria and fungi results in ___

physiological breakdown

Poor management of storage temperature accelerates ____ in fruits and vegetables.

remains almost unchanged or shows a steady decline

Respiration rate either ________________ until senescence intervenes, with little or no increase in ethylene production

freezing injury heat injury

Similar physiological damage of a commodity is also observed when storage temperatures cause freezing leading to ____, or excessively high temperatures leading to ___

1. change in the green color due to loss of chlorophyll, 2. browning of tissues due to changes in anthocyanin and phenolic compounds 3. development of yellow and red colors due to the development of anthocyanin and carotenoids, respectively. 4. physiological disorders and increased sensitivity to microbial spoilage.

The consequences of ethylene gas on the maturation process of fruits and vegetables includes:

loss of weight, but the textural quality is altered crispness and juiciness.

The loss of water from a commodity causes major deteriorative changes. Not only is there a ____, causing a commodity to lose its ___

respiratory peak

The major rise in ethylene production may take place before, just after or close to the _____

ketones, aldehydes, and alcohols.

The products of anaerobic respiration include

storage temperature, atmospheric oxygen, and carbon dioxide concentration

The rates of ethylene production vary for different fruits and may be controlled by _____, _____, and _____.

decrease in the product mass

The respiration process produces a ________________ as some of the food components are oxidized as well as a loss of sweetness in many commodities

ketones, aldehydes, and alcohols.

These products are often toxic to plant tissue and hasten its death and decay

• Undesired ripening and excessive softening of fruits in storage • Accelerated respiration rate • Accelerated senescence and loss of green color in leafy vegetables and immature fruit (e.g. cucumbers, tomatoes) • Undesirable discoloration • Sprouting (stimulation or retardation; e.g., potatoes) • Abscission of leaves (e.g., cauliflower, cabbage, foliage plants, etc.) • Reduction of storage life • Induction of phenolic synthesis

UNDESIRABLE ETHYLENE EFFECTS

aerobic

When oxygen is readily available, the respiration process is called ________________--

Ethylene (C2H4 )

a naturally occurring gas which participates in various biological processes in fruits

climacteric

an abrupt increase in the respiration rate is observed during ripening; it reaches a maximum (climacteric peak), followed by a rapid decrease

carotenoidss

are plant pigments responsible for bright red, yellow and orange hues in many fruits and vegetables.

anthocyanins

are plentiful in plant foods, providing the blue-violet colors of many fruits and vegetables.

Ethylene (C2H4 )

colorless and effective at very low concentrations

growth and development

ethylene can be produced in very small quantities by most of vegetables tissues, which require it for __________________, but it diffuses rapidly from the sites of production

uniform texture changes

ethylene favors ___________________ as the fruit ripen

anthocyanin and carotenoids chlorophyll degradation (degreening) and yellowing

ethylene stimulates color development with the synthesis of ____ and ____ , and ______ and _____

avocado, banana, breadfruit, cantaloupe, cherimoya, fig, guava, honeydew melon, jackfruit, kiwi fruit, mango, muskmelon, papaya, passion fruit (yellow), plantain, rambutan, sapote, soursop, watermelon, apple, tomato

examples of climacteric fruits

cashew apple, date, sweet passion fruit, grapefruit, lemon, lime, litchi, loquat, mandarin, mangosteen, olive, orange, pineapple, purple or red mombim, rose apple, starfruit, tangerine

examples of nonclimacteric fruits

nonclimacteric

fruit ripen only if they remain attached to the parent plant

respiration

is the conversion of starch and sugar in plant tissues to CO2 , water, and energy in the presence of O2 .

nonclimacteric

respiration rates show very little change during ripening

5°C-15°C.

the chilling injury occurs mostly in commodities from tropical and subtropical regions when they are stored at temperatures above their freezing point and below ____. This type of injury causes uneven ripening, decay, growth of surface molds, development of off-flavors, and both surface and internal discoloration.

depends on the maturity stage

the response to ethylene presence ______________ of the fruit

shorter

usually, the higher the respiration rate, the ____________ the shelf life of a fresh product is.

- Bitter principle (isocoumarin) in carrot roots - Toxic ipomeamarone in sweet potato roots - Russet spotting on lettuce - Lignification of asparagus

• Induction of phenolic synthesis